The number of homes listed for sale fell in August, led by a clutch of California cities that posted outsized declines.

Inventories fell in August by 1.2% from July, bucking a seasonal pattern of a slight uptick before the summer season ends. Listings were down by 18.7% from one year ago and 34.1% from two years ago, according to a report from Realtor.com.

Falling inventories are a leading driver behind the recent rally in home prices, and the declines point to continued price-strength in many parts of the Western U.S., which are also benefiting from strong investor demand.

Among the 15 cities with the largest year-over-year declines, some 13 were in California, led by Oakland, which posted a 58.4% decline. Other big declines came in Stockton (down 45%), Fresno (down 43.1%), Sacramento (down 42.4%), Riverside-San Bernardino (down 41.8%), Bakersfield (down 41.4%), and San Jose (down 41.1%).

Inventory declines have typically preceded stronger prices if demand stays the same, because more buyers are chasing fewer homes. But low inventory could also curb transaction volumes if buyers, frustrated by the lack of choice, sit on the sidelines.

The two metros outside of California with large declines were Atlanta and Seattle, where inventories fell by 41.1% and 37%, respectively.

Median asking prices, meanwhile, fell by 2.5% nationally from July and were nearly flat compared with one year ago. Asking prices were up from one year ago in 92 metros, flat in nine, and down from one year ago in 45.

The Realtor.com figures include sale listings from more than 900 multiple-listing services across the country.

Inventories tend to increase by around 2% in August over the past 28 years, according to Zelman & Associates, a research firm, as sellers make one last push before the beginning of the school year.